TOPIC: Shunt calculations

Hi,
I use a winch system made of 3 smartmotors (SM23165DT with brake option and i=20 gearbox) for moving a payload into X/Y/Z dimensions. It looks like a reversed tetrahedron, with the payload being at the intersection of the three winches strings. This is a "vertical application", so to speak the same language as the manual.

My concern is about motors generating voltage, and their protection. Our power supplies are at 48V, close to the maximum allowed.

How do I do the math for dimensioning the shunts ?

Is there a way to calculate voltage/current generation based on speed/load of the shaft ? Or some chart maybe.

The motors are 200W each. We are using about 50W-100W on each on average.

Maybe I can make a chart out of the load and speed. Is the Voltage constant a useful figure to calculate that ? I have some mechanical engineers at hand that can do the math if I get the input data right.